Study projects zoonosis hot spots

Most of the emerging infectious diseases in human medicine are zoonotic, or originate in animal populations. Some recent examples in the news include Middle Eastern respiratory syndrome (MERS), avian influenza and ebola. Diseases associated with cattle include brucellosis, bovine tuberculosis, rabies and others. Outbreaks among humans seem unpredictable, but researchers at the Cary Institute of Ecosystem Studies and the University of Georgia have developed a modeling system to help predict the risk of transmission of pathogens between mammals and humans.

The research team has developed a series of maps using data on 27 orders of terrestrial mammals known to carry pathogens that also infect humans. These include multiple species of rodents, primates, carnivores, bats, hoofed animals and others.

Conventional wisdom would suggest zoonotic diseases would be most prevalent in tropical areas with the most biodiversity. The researchers found that while potential zoonotic hosts are more numerous in the tropics, zoonotic diseases are more common in temperate regions.

Key findings in the study include:

More than 10% of rodent species are zoonotic hosts, carrying 85 unique zoonotic diseases. And although there are fewer species of primates overall, a greater proportion of primates, 21%, are zoonotic hosts.

Despite their species richness and bad reputation as prominent zoonotic reservoirs, bats carry just 25 zoonotic pathogens, compared with 85 for rodents, 61 for primates, 83 for carnivores and 59 for hooved mammals.

Europe and Russia are global hotspots for rodent hosts, while Central and South America are global hotpots for bat hosts; primate host richness is greatest in equatorial Africa.

Bacteria are the most common zoonotic pathogens, followed by viruses.

Results of the study, including the hot-spot maps, are published in the journal Trends in Parasitology.